The purpose of the proposed study is to develop an integrated transdiagnostic anxiety disorder treatment and standard smoking cessation treatment for smokers with anxiety disorders (who have been shown to be at high-risk for smoking cessation relapse). The intervention is designed to increase smoking cessation while reducing (1) anxiety symptoms, (2) depressive symptoms, and (3) the cognitive factor of Anxiety Sensitivity, thereby reducing three notable emotional risk factors of smoking cessation relapse and anxiety comorbidity, while at the same time targeting (4) nicotine withdrawal symptoms. The intervention development approach will follow a staged model consistent with NIH guidelines for developing and standardizing behavioral therapies. Accordingly, during the first year, startup activities will include piloting the integrated anxiety-smoking intervention on a subset of individuals, soliciting internal and external expert consultant and participant feedback, and development of the final treatment manual and procedures. The goal during this phase of the project will be to establish feasibility of treatment delivery, participant acceptability, and potetial for an effect. During the following 2 years, a two-arm efficacy study will be undertaken. The two arms of the randomized controlled trial (RCT) will be: (1) standard smoking cessation treatment and nicotine replacement therapy (NRT) plus a transdiagnostic cognitive-behavioral therapy for anxiety (Smoking Termination and Anxiety Reduction Treatment; START) or (2) standard smoking cessation treatment and nicotine replacement therapy plus contact control (ST+CTRL). The primary outcomes of this will be short- and long-term point prevalence abstinence (PPA) and time to first smoking lapse and time to smoking relapse.